Tracking a user's head position relative to a display enables a realistic presentation of 3D scenes through the use of motion parallax. Knowing the relative position of the user's head relative to the display a computer program can change the displayed views of 3D virtual objects and scenes. Accordingly, a user can inspect virtual 3D objects and scenes in a natural way by reproducing the way the user sees physical objects. However, head tracking relative to a display to view 3D image has limitations.
For example, a user of a flight simulation, would only be able to see views that the user would naturally see while flying the airplane. As such, during simulated flight, the user would not be able to leave the cockpit and inspect the plane.
The drawings referred to in this description should be understood as not being drawn to scale except if specifically noted.